For hypoxemic patients with chronic obstructive pulmonary disorder (COPD) and other restrictive lung diseases, continuous flow of supplemental oxygen has proven to improve survival and quality of life. Large patient care facilities often have large oxygen supplies, so conservation may not be a critical factor. Patients in hospitals are often prescribed 2 liters per minute, which is more than many patients require, especially when they are sedentary. In home settings, some patients are supplied with oxygen by means of an oxygen concentrator. Such devices are conventionally set at delivery rates which are sufficient for sedentary and moderately active patient requirements. The oxygen concentrators deliver oxygen at 6 PSI.
A major development in oxygen therapy was the introduction of oxygen conserving devices. Such include reservoir cannulas, pulse demand oxygen delivery devices, and transtracheal oxygen systems. Mobile patients, who carry pressurized oxygen tanks with them as they move around, are helped by oxygen conservation. These patients carry tanks with them, and the tanks are necessarily small. Conservation provides greater mobility. They can go greater distances for longer times, if the oxygen is conserved.
The essence of portable therapy is to permit the patient to be supplied with oxygen whether sedentary or active. There is a need for automatically adjusting the oxygen delivery to adapt to the patient's changing oxygen requirements. Systems which adjust to patient activity are more recent. One adaptive delivery device which is presently available is an electronic demand system with a motion sensor. The device is selectively set for sedentary or active. When the patient begins to exert, the device senses the motion and boosts delivery to the active setting. This device is only operative for pulse demand oxygen delivery. Many patients do not oxygenate well on pulse delivery systems and therefore require continuous oxygen flow. Examples of these patients include those with interstitial lung disease, severe COPD, and advanced lung cancer.
It is desirable to provide a continuous flow oxygen delivery device which regulates the amount of oxygen delivered to the patient in accordance with their physical activity.